The conformations, microdynamic behavior, and interactions with biologically important macromolecules of the neurohypophysial peptide hormones, hypothalamic hormone releasing factors, and other biologically active peptides will be investigated. The relationships between biological activity and function as a function of the conformations and microdynamic behavior of the peptides will be sought. Partially deuterated neurohypophysial hormones and related C14, C13 and unlabelled derivatives will be prepared, and similar luteinizing hormone releasing factor derivatives also will be prepared. Simplified preparations of deuterated amino acids will be studied. The deuterated hormones will be used to study the microdynamic behavior of these compounds and the interaction of the hormones with the carrier proteins, the neurophysins. Deuterium (H2) NMR methods will be used in these studies along with other physical methods including carbon-13 NMR, equilibrium thin film dialysis, and circular dichroism. Similar studies will be made on the hypothalamic peptide luteinizing hormone releasing factor. These studies will be used to develop a physical-chemical basis for understanding the significance of the conformations and microdynamic behavior of these peptides in various biological contexts.